Alternator battery questions

[sweet88gt]

This could be a long read but looking for insight.
2020 JLUR 28xxx miles auto 3.6 Tazer JL Lite for tire size and auto start/stop disabled. No Aux items installed

I have had issues with Batteries and Aux switch warnings for what I recall since 2021. In Dec I bypassed small battery and pulled fuse.
Friday coming home from work I get the Aux switch not available warning. I popped the hood and took a look around but didn't notice the dash was lit up until Saturday. Battery dead. Charged battery all day Sat and checked dash this morning after shutting all doors and gate. It went off. I just took it for a short drive and noticed on EVIC battery at 12.7 while driving. I have checked that before say back in Dec and it was 14 or above. Got home popped hood while running checked with my meter and only got 12 volts. Using my Fluke that I use for work it doesn't give me a good range. Tested the battery with my old school craftsman load tester and battery is good. Checked n7 fuse marked alternator and its good.

What else can I be looking for to test to see if a 28xxx mile alternator is actually not working ? Is there another fuse Im missing?

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[sweet88gt]

To add I searched and found information about the IBS sensor. Also found that a fully charged battery will only read 12.6-12.7 volts. As the battery degrades the IBS system will increase voltage.
Does this seem correct ?
On my way home today it stayed in the 12.7-12.8 range and for a brief minute AC on it ran up to 14 volts on the EVIC.
Seems Im a bit older and not familiar with smart alternators or charging systems.

 

[ecidiego]

IBS thinks you're fully charged = normal. Leave your headlights on for 20 minutes with the car off. Then start it and report back.

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